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35 Cards in this Set
- Front
- Back
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What are the three types of muscle? |
• Skeletal • Cardiac • Smooth |
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What defines skeletal muscle? |
• It is under conscious control - voluntary • It is attached to the bones to allow movement • It gives the body form and contours • Appears to have lines in it – striated • Each cell has many nucleus’ – multi nucleated • The nuclei are all at the periphery (outside) |
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What defines smooth muscle? |
• Smooth muscle is found in our organs, blood vessels and in the uterus • It is involuntary • It is smooth in appearance (no striations) • Nucleus is cigar shaped • Smaller than skeletal muscle |
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What defines cardiac muscle? |
• Cardiac muscle makes up the heart • Cardiac muscle is involuntary • Each fibre is branched so it contracts in all directions at once • Striated in appearance, but the striations are not as organised as in skeletal muscle • Each cell has a single nucleus and it is in the centre of each cell •Has intercalated discs where two muscle fibres meet |
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What are all muscles three major properties? |
• They can contract • They have extensibility • They can stretch • They have elasticity • They will return to their original shape |
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What role do ligaments play? |
• attach bone to bone |
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What role do tendons play? |
• attach bone to muscle |
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What two muscles accommodate movement? |
• Agonist and Antagonist |
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Define origin |
• where the muscle joins to a fixed bone |
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Define insertion |
• where the muscle is joined to a moveable bone |
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Define belly |
• the thick, fleshy part of the muscle |
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Define flexor |
• the muscle that brings about flexion |
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Define extensor |
• the muscle that brings about extension |
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Define agonist |
• The muscle that causes the desired action is called the agonist or prime mover |
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Define antagonist |
• The muscle that opposes the action of the agonist |
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Define a Synergist |
• a muscle that helps movement indirectly by stabilising a joint • E.g. muscles stop the wrist from flexing when you clench your fist |
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Define Fixator |
• the muscle that immobilises the joint |
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Define muscle fibre |
• muscle cell |
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Define sarcolemma |
• the cell membrane of a muscle cell |
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Define Sarcoplasm |
• the cytoplasm of a muscle cell |
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Define myofibril |
• fibres that run parallel in muscle fibres that generate force • Myofibrils are composed of smaller subunits called myofilaments |
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Define myofilament |
made of protein and generate the force of contraction |
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What are the 2 types of myofilament |
• Actin • Myosin |
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Define Sarcomere |
• the functional unit of a myofilament |
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Thick or thin actin myosin |
• Actin Thin myofilaments • Myosin Thick myofilaments |
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What happens when an action potential reaches a muscle? |
• energy is supplied to ,the actin and myosin, and they slide past each other to generate force by shortening the myofibril • This is called the sliding filament model |
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What is the sliding filament model? |
• When muscles contract the sarcomeres shorten • The sarcomeres shorten when the actin and myosin slide over each other • The thin actin filaments slide over the thick myosin filaments |
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What happens to the structure of the model? |
• The Z lines come closer together • The I bands become shorter • The A bands stay the same length • The myofilaments stay the same length, they just slide over (overlap) one another! |
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What is ATP used for? |
• ATP is used to allow the myosin to bind/attach to the actin |
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What is a T- tubule |
• The skeletal muscle has “pits” |
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What is the sarcoplasmic reticulum? |
• an internal calcium (Ca2+) store |
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What is troponin and what is it's function? |
• A protein that stops muscles contracting on their own by binding to actin |
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How does a skeletal muscle contract? |
1. ACh is released from the pre-synaptic membrane 2. ACh diffuses across the synapse to bind with the receptor (M3) on the post-synaptic membrane 3. Depolarisation of the muscle’s cell membrane (sarcolemma) 4. Depolarisation spreads into the T tubule 5. Sarcoplasmic reticulum (SR) releases calcium through voltage gated Ca2+ channels 6. Calcium levels near the sarcomeres increases 7. Calcium removes Troponin from the actin (removes the inhibition) Changing the conformation of the Troponin-Tropomyosin complex 8. Myosin heads can now bind to the actin, pulling the actin towards the centre of the sarcomere Shortening of the length of the sarcomere (Z lines come closer togerther) 9. This is known as cross-bridging 10. This mechanism is powered by the use of ATP (ATP changes the position of the myosin head) |
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The muscle contraction ceases when |
1. ACh is destroyed by enzymes in the synapse 2. Ca2+ is reabsorbed by the SR 3. Troponin rebinds to actin |
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How does Calcium allow the cross bridging to take place? |
• Calcium comes from the sarcoplasmic reticulum when its membrane is depolarised • A troponin/tropomyosin complex blocks the actin binding sites • Calcium attaches to the troponin changing its conformation • This makes tropomyosin also move to expose the binding sites on the actin • This allows myosin to attach to the actin • Myosin can only attach to the actin IF calcium binds to the troponin and allows tropomyosin to move |
